This disclosure relates generally to the detection of ice or ice crystals in the atmosphere.
Hazardous weather is generally associated with convective weather cells. Convective weather cells can produce turbulence, high winds, lightning, hail, and other weather hazards. In addition, convective cells can provide large updrafts that loft large amounts of moisture to higher altitudes (e.g., high portions troposphere). The moisture can be super cooled liquid at temperatures much colder than the freezing point of water because the water was lofted quickly by the updraft and has not encountered condensation nuclei upon which to crystallize as ice.
Non-convective rain clouds (e.g., stratiform rain) can also include ice crystals. Non-convective rain clouds are striated with temperature. At low altitudes where the temperature is above the freezing point, liquid water is present as rain. At high altitudes where the temperature is below the freezing point, ice crystals form.
Conventional aircraft hazard weather radar systems, such as the WXR 2100 MultiScan™ radar system manufactured by Rockwell Collins, Inc., have Doppler capabilities and are capable of detecting at least four parameters: weather range, weather reflectivity, weather velocity, and weather spectral width or velocity variation. The weather reflectivity is typically scaled to green, yellow, and red color levels that are related to rainfall rate. The radar-detected radial velocity variation can be scaled to a turbulence level and displayed as magenta. Such weather radar systems can conduct vertical sweeps and obtain reflectivity parameters at various altitudes and can detect the presence of ice using reflectivity parameters and temperature. However, such detection of ice cannot be performed at longer ranges. In some embodiments, the radar may be a single frequency radar (e.g., X-band radar) or a multi-frequency radar (e.g., a radar with both X-band and Ka-band frequencies). In some embodiments, the single or multi-frequency radar may include polarization diversity capabilities.
Ice or ice crystal formation at high altitudes can pose various threats to aircraft. Flying through ice or ice crystal formation at high altitudes can cause engine roll back, engine stall, engine flameout, and incorrect airspeed measurements. Detecting areas of ice and ice crystal formation at longer ranges is desirable so that pilots can avoid such areas.
Thus, there is a need for a system and method for more accurate, long range detection of ice and/or ice crystals high in the troposphere. There is also a need for inferring the existence of ice and/or ice crystals based on the detection and analysis of convective cells or hazards associated therewith. There is also a need to distinguish highly convective ice crystal formation areas form non-convective stratiform rain areas that do not produce high altitude ice crystals. Further still, there is a need to detect and locate convective cells by measuring the amount of moisture (e.g., liquid water, such as total water content) present at altitudes where the temperature is below the freezing point. Yet further, there is a need for an aircraft hazard warning system optimized to determine the location and presence of large areas of high altitude ice resulting from convective cell blow off. Further, there is a need for an aircraft hazard warning system that includes inferential ice detection and location.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.